Formatting Output with Invoke-Command

PS> Invoke-Command $computers { Get-ExecutionPolicy } |
      Format-Table PSComputerName, Value

PSComputerName  Value                     
--------------  -----                     
Computer1       Restricted                
...

As BACON points out in comments on the question, it is Invoke-Command that implicitly adds the PSComputerName and RunSpaceId properties to the objects returned by the script block ({ ... }) run on each target computer, and whether they are displayed by default depends on the type of the object returned.
In the case of the [Microsoft.PowerShell.ExecutionPolicy] instances returned by Get-ExecutionPolicy, they are displayed by default, which means that in order to display only the properties of interest you need an explicit Format-* call.

Note that an automatically added Value property is an artifact of the remotely executed script block returning an instance of an [enum]-derived type, such as the instances of [Microsoft.PowerShell.ExecutionPolicy] returned by Get-ExecutionPolicy.

Remotely invoked Invoke-Command script blocks outputting non-primitive-.NET-type instances return deserialized objects of type Deserialized.<original-type-name>.
[enum]-derived instances result in a deserialized type with a Value property defined as a ScriptProperty member with signature System.Object Value {get=$this.ToString();}; for general information about how serialization and deserialization works in PowerShell remoting and background jobs, see this answer.

General tips:

• Write-Output is generally not needed, because the output of any statement that is not captured in a variable or redirected to a file / to $null is implicitly sent to the output stream.

• If you ever need to write cross-platform-compatible code, avoid aliases such as write, because they won't work as expected on Unix-like platforms in PowerShell Core, where aliases that would shadow native utilities aren't defined.